It has long been considered desirable to provide linerless postage stamps with pressure sensitive adhesive. Pressure sensitive adhesive postage stamps are becoming increasingly popular, but heretofore have always required a release sheet because if a conventional release liner is applied to the top face of the postage stamp (which is necessary to allow stacking of the stamps or formation into a roll configuration), the cancellation pattern applied by the USPS automated equipment has a tendency to not stick to the top face of the stamp, but rather to be wiped off during further handling, because the cancellation ink cannot be absorbed by, or otherwise retained by, the top face of the stamp. If a very light coating of release material is applied to the top of the stamp, then--particularly if the stamps are not stored under ideal conditions--the adhesive from one stamp may stick to the top face of another causing obliteration of the stamp indicia, making it unsuitable for its intended purpose.
According to the present invention the above mentioned problem is solved and it is possible to produce linerless postage stamps which have a top face that will appropriately hold cancellation ink when applied in a cancellation pattern so that the cancellation pattern is visible and will not wipe off during normal handling.
According to one aspect of the present invention, a method of making a linerless postage stamp from a sheet or web having top and bottom faces is provided. The method comprises: (a) Applying a pressure sensitive adhesive to the bottom face. (b) Applying to the top face a release coat for the adhesive applied in (a) in fluid form with an effective amount of stamp cancellation ink retaining particles therein, so that when the release coat solidifies on the top face and is contacted by stamp cancellation ink the particles will retain sufficient stamp cancellation ink so that the ink is visible on the top face once applied and dried, and will not be wiped off during normal handling. And, (c) forming the web or sheet into separate postage stamps with postage stamp indicia on a top face.
Preferably (c) is practiced by (c1) applying postage stamp indicia to the top face prior to the practice of (b); and (c2) forming lines of weakness in the sheet or web to define the boundaries of separable individual stamps. Typically (c2) is practiced before (b). Desirably (b) is practiced utilizing particles selected from the group consisting essentially of fumed silica, colloidal silica, solid fluoropolymer lubricant, calcium carbonate, and titanium dioxide, or combinations thereof. That is (b) may be practiced by using silicone release coat containing between about 3-7% by weight of the release coat of fumed silica; or (b) may be practiced using silicone release coat containing between about 4-40% by weight of the release coat of colloidal silica. The release coat may be thermo-curable silicone, but preferably is UV curable silicone applied at a weight of between about 0.2-1.5 pounds per ream. Typically the stamp made is a canceled stamp, and the method further comprises applying the adhesive on the bottom face to a mailing piece, and applying cancellation ink in the form of a cancellation image to the top surface of the stamp, the ink absorbed by the particles to provide a visible cancellation image that does not wipe off during normal automated processing and manual handling of the mailing piece.
According to another aspect of the present invention a canceled postage stamp is provided comprising the following the components: A substrate having top and bottom surfaces. Postage stamp indicia imaged on the top face. A pressure sensitive adhesive coating on the bottom face. An adhesive release coat, to which the pressure sensitive adhesive will not non-releasably adhere, on the top face having an effective amount of stamp cancellation ink retaining particles therein. Stamp cancellation ink in a cancellation pattern on the release coat. And, the effective amount of ink retaining particles retaining sufficient stamp cancellation ink so that the pattern is readily visible and the ink is not wiped off during normal handling of a mailing piece containing the substrate. The details of the release coat and particles preferably are as described above.
According to another aspect of the present invention a postage stamp is provided comprising: A paper substrate having top and bottom faces. A pressure sensitive adhesive on the bottom face. Postage stamp indicia on the top face. And, a silicone release material on the top face having more than a trace amount of particles consisting essentially of calcium carbonate, titanium dioxide, fumed silica, kaolin clay, aluminum oxide, wollastonite, talc, and colloidal silica, or combinations thereof. Preferably the details of the release coat, particles, etc., are as described above.
According to yet another aspect of the present invention, a linerless postage stamp assembly is provided comprising: A web of a plurality of postage stamps comprising a substrate material with pressure sensitive adhesive on a first face, and having a second face with release material which will not adhere to the adhesive but will absorb or otherwise retain stamp cancellation ink substantially permanently in sufficient quantity so that a cancellation pattern thereof is clearly visible. The web is a roll configuration with adhesive of one stamp engaging release material of another, each stamp connected to adjacent stamps by lines of weakness. And, stamp cancellation ink absorbing particles provided in the release material.
It is the primary object of the present invention to provide a linerless postage stamp that can effectively retain the cancellation pattern applied thereto. This and other objects of the invention will become apparent from the detailed description of the invention and from the appended claims.